" If you have been changing the oil at 12,000 miles, you should change the interval to 7500 miles"
If he has actually been using a 12k interval for oil changes, I would suggest that he do at least two oil changes at a 2k mile interval, and then–perhaps–go to a 7.5k interval. This might not undo the damage of 12k oil changes, but…it might help.
Well, I was wondering all along just what engine you have. The 4 cylinder would have a timing belt as so would the 3.0 liter V6. The other V6s have timing chains which should last the life of the engine. (Of course, if the belt breaks on the 4 cylinder, that will be the “life of the engine”).
If your engine is an interference type do it NOW. Stop putting it off, you’ll pay for it later if you do. Rocketman
This posting is one reason why I would worry about buying a used car . . . who would take care of a vehicle this way, who knows? Problem is, many people do this and then sell their car, and others are stuck with the problem vehicle. Rocketman
Agreed, @rocketman . OP is not at all alone in doing things like letting the oil light come on and off for 3 years before doing anything about it. Whenever I buy a used car, I look it over VERY carefully and then still assume I might have to spend some money fixing problems caused by the previous owner’s neglect.